In a prior art steering device in a riding mower, use is made of a steering wire which is wound around a rotatable steering column and extends over two first deflecting wheels arranged on both sides of the steering column and located in a common plane, and two second deflecting wheels arranged on both sides of the steering column and located in a second and a third plane, respectively, which is substantially orthogonal relative to this common plane, to a steerable wheel assembly, to which it is connected. This steering device suffers from the essential drawback that the steering wire is rapidly worn especially in the portion thereof extending over the steering column, but also in the portions extending over the first and the second deflecting wheels. This results in a frequent breaking of the steering wire, thus necessitating replacement.
In order to reduce this drawback, that part of the steering wire which extends over the steering column and the two first deflecting wheels has been replaced in a known steering device, which is of the type described by way of introduction, with a transmission chain extending over a steering sprocket nonrotatably connected to the steering column and located in the same plane as the first two deflecting wheels which here consist of sprockets. This chain is, at each end, connected to a steering wire which like before extends over the respective second deflecting wheels to the steerable wheel assembly. In this prior art steering device, the wear in the area of the steering column is eliminated. The wear problem, however, remains for the steering wires which extend over the second two deflecting wheels and which therefore break relatively frequently.
In order to eliminate this wear problem too, each of the flexible steering cables in a steering device, known from WO 95/31891, has been formed as a transmission chain which is, between the steering sprocket and the respective deflecting wheels, coupled, by means of a link element, to the chain, flexible in the plane of the steering sprocket, so as to form a straight line with said chain, the link element having a first hinge pin to which an end link in one of these two chains is articulated, and a second hinge pin to which an end link in the other of these two chains is articulated, said two hinge pins being angled relative to each other at an angle equalling the angle, preferably 90°, at which the second and the third plane, respectively, is angled relative to the plane of the steering sprocket.
Regardless of the transmission cable and the steering cables being steering wires or transmission chains, the force, which, in these known steering devices, with the aid of a hand wheel has to be applied to the steering column to make it pivot the wheel assembly, is very large, making it rather difficult to operate the implement carrier.